1. Field of the Invention
The present invention relates to a silicone microparticle formed of a silicone elastomer spherical microparticle covered with a polyorganosilsesquioxane, and a method for producing the same.
2. Description of the Related Art
With regard to a silicone microparticle, a microparticle having a rubber elasticity (silicone elastomer microparticle) and a microparticle of a polyorganosilsesquioxane resin have been known; and for example, in order to enhance a resistance to cracking of a package caused by stress due to thermal expansion of an electric part, an attempt has been made to blend a silicone elastomer microparticle into a thermosetting resin such as an epoxy resin used for packaging of an electric and an electronic part. However, a silicone elastomer microparticle has high agglomeration tendency and poor dispersibility into a resin so that a stress relaxation effect cannot be obtained fully; and thus, there has been a problem of decreasing a strength of the resin.
To solve the problem as mentioned above, inventors of the present invention proposed a silicone microparticle formed of a silicone elastomer spherical microparticle covered with a polyorganosilsesquioxane (Japanese Patent Laid-Open No. H07-196815); this silicone microparticle has a rubber elasticity and is characterized by low agglomerating tendency and excellent dispersibility into a substrate.
In addition, the silicone microparticle formed of a silicone elastomer spherical microparticle covered with a polyorganosilsesquioxane shown in Japanese Patent Laid-Open No. H07-196815 can be easily broken to primary particles because of low agglomerating tendency; and thus, it can be classified by a dry process with high efficiency. On the other hand, in a silicone elastomer microparticle having high agglomerating tendency, classification thereof is difficult.
In order to provide a cosmetic with a use feeling such as non-stickiness and smoothness and with a spreading property, a silicone microparticle is used. Especially the silicone microparticle formed of a silicone elastomer spherical microparticle covered with a polyorganosilsesquioxane shown in Japanese Patent Laid-Open No. H07-196815 gives a soft feeling, lacks in agglomerating tendency, and has excellent dispersibility; and thus, it is used in many cosmetics.
However, for example, in order to enhance a stress relaxation effect and a soft feeling further, if rubber hardness of the silicone elastomer spherical microparticle portion of the silicone microparticle formed of a silicone elastomer spherical microparticle covered with a polyorganosilsesquioxane shown in Japanese Patent Laid-Open No. H07-196815 is made lower or particle diameter thereof is made smaller, there appears a problem of higher agglomerating tendency and lower dispersibility.